1. Field of the Invention
The present invention relates to an Infrared Radiation (IR) sensing device, and more particularly, to an IR sensing device by means of overlaying one or more Color Filter Arrays (CFA) along with the optical coating for passing IR and filtering non-IR out.
2. Description of the Prior Art
IR sensing devices based on silicon technology typically require the use of a non-infrared blocking element somewhere in the optical chain for only responding IR. The purpose of this element is to prevent non-infrared radiation (IR) or light (typically considered to be light with a wavelength longer than 780 nm) from entering the optical sensors of the optical sensing devices. Silicon-based optical sensors, e.g. Charge Coupled Device (CCD) sensor or a Complementary Metal-Oxide-Semiconductor (CMOS) sensor, will typically be sensitive to light with wavelengths up to approximately 1000 nm. If the non-IR (visible light) is permitted to enter the optical sensor, the IR sensing device will respond to the non-IR, and generate an output signal. Since the purpose of the IR sensing device is to create a representation of IR present in a scene, the non-IR will introduce a false response.
A common method for preventing these difficulties is to use a thin-film optical coating on glass to create an optical element which blocks visible light (typically from 400 nm to 780 nm) and passes the IR. However, to block light with such wide range (400 nm to 780 nm), the number of the layers of the optical coating is larger, e.g. 45. Since the number of the layers of the optical coating has to be so large to achieve the capability of filtering out the non-IR, which deteriorates the malleability and the flexibility of the optical coating, the optical coating can not be coated on the lens nor the optical sensor consequently. Therefore, the conventional IR sensing device realized with the optical coating comes with high cost and difficulty for production, which is inconvenient.